Pulley for alternator

ABSTRACT

The present invention relates to a pulley for an alternator, and in particular, to a pulley applicable to an automotive alternator. The pulley effectively mitigates the problem that a belt and a tension pulley of an alternator vibrate because a rotation speed of a vehicle engine changes, thereby improving the overall operating efficiency of the alternator and the service life of the working belt and the tension pulley.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from Taiwan patentapplication TW 103 124 194, filed Jul. 14, 2014, the contents of whichare herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a pulley for an alternator, and inparticular, to a pulley for an automotive alternator.

An alternator is a type of generator that can produce an alternatingcurrent by converting mechanical energy into electrical energy. Anautomotive alternator converts mechanical energy of an engine intoelectrical energy to charge a battery, so as to supply electrical powerto other electrical appliances on the automobile, and start a motor torotate the engine.

An alternator generally has an annular stator and a rotor received inthe annular stator. A wire is wound on the stator, and the rotor rotatesrapidly in the stator so that the wire moves relative to a magneticfield generated by the rotor, and an induced electromotive force(voltage) is generated in the wire.

An automotive alternator is usually utilized by an engine driving abelt. The belt is wound on a pulley, and the pulley is connected to arotor so as to drive the rotor to rotate. However, in conventionalalternator design, when an engine starts, or accelerates or deceleratesquickly in an instant, a waveform changes significantly at the momentthe generator charges a battery, and it cannot be stabilized. Inaddition, one side of the belt wound on the pulley is tight, and theother side thereof is slack. The tension of the slack-side belt is low,and therefore a tensioner is disposed thereon to adjust the tension ofthe belt. However, when a rotation speed at which the engine transmitspower changes suddenly, because the pulley of the generator is locked bya nut and the belt is made of a flexible material and cannot reflect therotation speed immediately, a slip is easily caused between the belt andthe pulley. Moreover, the fluctuation of the rotation speed causes thebelt to bear not only a repeated stress but also a centrifugal forcethat is applied on the belt when the pulley rotates. The value of thecentrifugal force changes with the rotation speed, and therefore thebelt is often affected by adverse factors of an internal micro tension,which pulls the belt, and external large-amplitude shaking.

SUMMARY

The present invention provides a pulley for an alternator, whichincludes an outer wheel, provided with an axle hole at the center; aclutch wheel, fixedly disposed in the axle hole of the outer wheel andhaving a pivot hole; a hollow connecting shaft, having a first end and asecond end, where the first end is rotatably disposed in the pivot holeof the clutch wheel, so that the hollow connecting shaft maintains aco-rotational relationship with the outer wheel in a first relativerotation direction by means of the clutch wheel, while in a secondrelative rotation direction, the hollow connecting shaft isdisassociated from the co-rotational relationship with the outer wheel,and presents an idling state; and the second end of the hollowconnecting shaft is provided with a first protruding portion; a hollowcore shaft, having a first end and a second end, where the hollow coreshaft is rotatably received in the outer wheel, and the second end ofthe hollow core shaft is rotatably arranged at the second end of thehollow connecting shaft; the second end of the hollow core shaft isprovided with a second protruding portion, and the second protrudingportion corresponds to the first protruding portion; the number of oneof the first protruding portion and the second protruding portion is atleast one, and the number of the other of the first protruding portionand the second protruding portion is at least two; and an elasticelement, disposed between the second end of the hollow connecting shaftand the second end of the hollow core shaft.

When an external force drives the outer wheel to rotate, the outer wheelrotates relative to the hollow connecting shaft in the first relativerotation direction, and drives, through the clutch wheel, the hollowconnecting shaft to rotate synchronously; the second end of the hollowconnecting shaft presses the elastic element, and while being pressed,the elastic element pushes the second end of the hollow core shaft,thereby driving the hollow core shaft to rotate; and if a rotation angleof the hollow connecting shaft relative to the hollow core shaft exceedsa predetermined value at this time, the first protruding portion of thehollow connecting shaft contacts the second protruding portion of thehollow core shaft, thereby stopping relative rotation between the hollowconnecting shaft and the hollow core shaft, so as to prevent the elasticelement from being pressed excessively, and to set the hollow connectingshaft and the hollow core shaft in a synchronous co-rotationalrelationship. When the external force decreases or stops driving theouter wheel to rotate, the hollow core shaft continues to rotate due toinertia, and stretches the elastic element, and while being stretched,the elastic element pulls the second end of the hollow connecting shaft,thereby driving the hollow connecting shaft to rotate relative to theouter wheel in the second relative rotation direction, so that thehollow connecting shaft is disassociated from the co-rotationalrelationship with the outer wheel, and idles in the clutch wheel; and ifa rotation angle of the hollow connecting shaft relative to the hollowcore shaft exceeds a predetermined value at this time, the firstprotruding portion of the hollow connecting shaft contacts the secondprotruding portion of the hollow core shaft, thereby stopping relativerotation between the hollow connecting shaft and the hollow core shaft,so as to prevent the elastic element from being stretched excessively,and to set the hollow connecting shaft and the hollow core shaft in asynchronous co-rotational relationship.

According to another preferred embodiment of the present invention, thehollow core shaft passes through the hollow connecting shaft, and thefirst end of the hollow core shaft protrudes from the first end of thehollow connecting shaft; a tight-fit component is sleeved over an outercircumferential wall surface of the first end of the hollow core shaftin a tight-fit manner, and the tight-fit component is also tightly fitwith an end surface of the first end of the hollow connecting shaft;therefore, the hollow connecting shaft and the hollow core shaft aremade to corotate coaxially under a friction between the tight-fitcomponent and the hollow connecting shaft and a friction between thetight-fit component and the hollow core shaft, and when the externalforce decreases or stops driving the outer wheel to rotate, the hollowcore shaft continues to rotate due to inertia, and drives, through thetight-fit component, the hollow connecting shaft to rotate relative tothe outer wheel in the second relative rotation direction, so that thehollow connecting shaft is disassociated from the co-rotationalrelationship with the outer wheel and idles in the clutch wheel.

According to another preferred embodiment of the present invention, thetight-fit component is a C-shaped retaining ring.

According to another preferred embodiment of the present invention, afirst ball bearing is sleeved over the first end of the hollow coreshaft, a second ball bearing is sleeved over the second end of thehollow core shaft, and the first ball bearing and the second ballbearing are disposed between the hollow core shaft and the outer wheel,so that the hollow core shaft is rotatable relative to the outer wheel.

According to another preferred embodiment of the present invention,three grooves are provided in a concave manner on an innercircumferential wall surface of the outer wheel, and an anaerobicadhesive is coated in the grooves, so that the clutch wheel, the firstball bearing, and the second ball bearing are separately tightly fit inthe grooves, and are fixedly glued in the outer wheel by using theanaerobic adhesive.

According to another preferred embodiment of the present invention, apositioning casing is further sleeved over the first ball bearing, andan axial position of the pulley on the alternator is limited by thepositioning casing.

According to another preferred embodiment of the present invention, anouter circumferential wall surface of the outer wheel is provided with abelt groove, for a belt to be wound on.

According to another preferred embodiment of the present invention, thebelt is connected to a mechanical energy generating source, and themechanical energy generating source provides an external force to drivethe belt, thereby driving the outer wheel to rotate.

According to another preferred embodiment of the present invention, themechanical energy generating source is an engine.

According to another preferred embodiment of the present invention, aninner circumferential wall surface of the hollow core shaft is providedwith a threaded surface, the threaded surface is screwed with a jointlever having corresponding threads, and the joint lever is connected toa rotor, so that the hollow core shaft and the rotor corotatesynchronously.

According to another preferred embodiment of the present invention, aninner circumferential wall surface of the outer wheel is provided with astep portion, for the clutch wheel to abut against, thereby limiting anaxial displacement of the clutch wheel.

According to another preferred embodiment of the present invention, oneend of the clutch wheel is provided with a positioning member, to limitan axial position of the clutch wheel, and the positioning member is aC-shaped retaining ring.

According to another preferred embodiment of the present invention, theelastic element is a torque spring, and a wire profile of the torquespring is circular, elliptical, or rectangular.

According to another preferred embodiment of the present invention, whenthe wire profile of the torque spring is rectangular, two end surfacesof the torque spring are grinded, so as to enhance axial positioning ofthe torque spring and control a free length of the torque spring moreprecisely.

According to another preferred embodiment of the present invention, twosides of the clutch wheel are each provided with an oil seal element, soas to prevent liquid in the clutch wheel from flowing into the outerwheel.

According to another preferred embodiment of the present invention, oneside of one of the oil seal elements is provided with a positioningmember, and the positioning member is sleeved over an inner side wallsurface of the outer wheel in a tight-fit manner, to limit axialpositions of the oil seal elements.

According to another preferred embodiment of the present invention, thepositioning member is a C-shaped retaining ring.

According to another preferred embodiment of the present invention, anend, corresponding to the second end of the hollow core shaft, of theouter wheel is arranged with a dust cover, so as to prevent externaldust from entering the outer wheel.

The present invention further provides a pulley for an alternator, whichincludes an outer wheel, provided with an axle hole at the center; aclutch wheel, fixedly disposed in the axle hole of the outer wheel andhaving a pivot hole; a hollow connecting shaft, having a first end and asecond end, where the first end is rotatably disposed in the pivot holeof the clutch wheel, so that the hollow connecting shaft maintains aco-rotational relationship with the outer wheel in a first relativerotation direction by means of the clutch wheel, while in a secondrelative rotation direction, the hollow connecting shaft isdisassociated from the co-rotational relationship with the outer wheel,and presents an idling state; and the second end of the hollowconnecting shaft is provided with a first protruding portion; a hollowcore shaft, having a first end and a second end, where the hollow coreshaft is rotatably received in the outer wheel, and the hollow coreshaft passes through the hollow connecting shaft; the first end of thehollow core shaft protrudes from the first end of the hollow connectingshaft, and the second end of the hollow core shaft is rotatably arrangedon the second end of the hollow connecting shaft; the second end of thehollow core shaft is provided with a second protruding portion, and thesecond protruding portion corresponds to the first protruding portion;the number of one of the first protruding portion and the secondprotruding portion is at least one, and the number of the other of thefirst protruding portion and the second protruding portion is at leasttwo; an elastic element, disposed between the second end of the hollowconnecting shaft and the second end of the hollow core shaft; and atight-fit component, sleeved over an outer circumferential wall surfaceof the first end of the hollow core shaft in a tight-fit manner andtightly fit with an end surface of the first end of the hollowconnecting shaft, so that the hollow connecting shaft and the hollowcore shaft corotate coaxially under a friction between the tight-fitcomponent and the hollow connecting shaft and a friction between thetight-fit component and the hollow core shaft.

When an external force drives the outer wheel to rotate, the outer wheelrotates relative to the hollow connecting shaft in the first relativerotation direction, and drives, through the clutch wheel, the hollowconnecting shaft to rotate synchronously, and the hollow connectingshaft drives, through the tight-fit component, the hollow core shaft torotate; if the friction provided by the tight-fit component isinsufficient to drive the hollow core shaft to rotate at this time, thesecond end of the hollow connecting shaft presses the elastic element,and while being pressed, the elastic element pushes the second end ofthe hollow core shaft, thereby driving the hollow core shaft to rotate;and if a rotation angle of the hollow connecting shaft relative to thehollow core shaft exceeds a predetermined value at this time, the firstprotruding portion of the hollow connecting shaft contacts the secondprotruding portion of the hollow core shaft, thereby stopping relativerotation between the hollow connecting shaft and the hollow core shaft,so as to prevent the elastic element from being pressed excessively, andto set the hollow connecting shaft and the hollow core shaft in asynchronous co-rotational relationship. When the external forcedecreases or stops driving the outer wheel to rotate, the hollow coreshaft continues to rotate due to inertia, and drives, through thetight-fit component, the hollow connecting shaft to rotate relative tothe outer wheel in the second relative rotation direction; and if thefriction provided by the tight-fit component is insufficient to drivethe hollow connecting shaft to rotate at this time, the hollow coreshaft rotates relative to the hollow connecting shaft until the firstprotruding portion of the hollow connecting shaft contacts the secondprotruding portion of the hollow core shaft, thereby stopping relativerotation between the hollow connecting shaft and the hollow core shaft,and setting the hollow connecting shaft and the hollow core shaft in asynchronous co-rotational relationship.

According to another preferred embodiment of the present invention, whenthe external force decreases or stops driving the outer wheel to rotate,the hollow core shaft continues to rotate due to inertia, and drives,through the tight-fit component, the hollow connecting shaft to rotaterelative to the outer wheel in the second relative rotation direction;if the friction provided by the tight-fit component is insufficient todrive the hollow connecting shaft to rotate at this time, the hollowcore shaft stretches the elastic element, and while being stretched, theelastic element pulls the second end of the hollow connecting shaft,thereby driving the hollow connecting shaft to rotate relative to theouter wheel in the second relative rotation direction, so that thehollow connecting shaft is disassociated from the co-rotationalrelationship with the outer wheel; and if a rotation angle of the hollowconnecting shaft relative to the hollow core shaft exceeds apredetermined value, the protruding portion of the hollow connectingshaft contacts the protruding portion of the hollow core shaft, therebystopping relative rotation between the hollow connecting shaft and thehollow core shaft, so as to prevent the elastic element from beingstretched excessively, and to set the hollow connecting shaft and thehollow core shaft in a synchronous co-rotational relationship.

According to another preferred embodiment of the present invention, thetight-fit component is a C-shaped retaining ring.

According to another preferred embodiment of the present invention, afirst ball bearing is sleeved over the first end of the hollow coreshaft, a second ball bearing is sleeved over the second end of thehollow core shaft, and the first ball bearing and the second ballbearing are disposed between the hollow core shaft and the outer wheel,so that the hollow core shaft is rotatable relative to the outer wheel.

According to another preferred embodiment of the present invention,three grooves are provided in a concave manner on an innercircumferential wall surface of the outer wheel, and an anaerobicadhesive is coated in the grooves, so that the clutch wheel, the firstball bearing, and the second ball bearing are separately tightly fit inthe grooves, and are fixedly glued in the outer wheel by using theanaerobic adhesive.

According to another preferred embodiment of the present invention, apositioning casing is further sleeved over the first ball bearing, andan axial position of the pulley on the alternator is limited by thepositioning casing.

According to another preferred embodiment of the present invention, anouter circumferential wall surface of the outer wheel is provided with abelt groove, for a belt to be wound on.

According to another preferred embodiment of the present invention, thebelt is connected to a mechanical energy generating source, and themechanical energy generating source provides an external force to drivethe belt, thereby driving the outer wheel to rotate.

According to another preferred embodiment of the present invention, themechanical energy generating source is an engine.

According to another preferred embodiment of the present invention, aninner circumferential wall surface of the hollow core shaft is providedwith a threaded surface, the threaded surface is screwed with a jointlever having corresponding threads, and the joint lever is connected toa rotor, so that the hollow core shaft and the rotor corotatesynchronously.

According to another preferred embodiment of the present invention, aninner circumferential wall surface of the outer wheel is provided with astep portion, for the clutch wheel to abut against, thereby limiting anaxial displacement of the clutch wheel.

According to another preferred embodiment of the present invention, oneend of the clutch wheel is provided with a positioning member, to limitan axial position of the clutch wheel, and the positioning member is aC-shaped retaining ring.

According to another preferred embodiment of the present invention, theelastic element is a torque spring, and a wire profile of the torquespring is circular, elliptical, or rectangular.

According to another preferred embodiment of the present invention, whenthe wire profile of the torque spring is rectangular, two end surfacesof the torque spring are grinded, so as to enhance axial positioning ofthe torque spring and control a free length of the torque spring moreprecisely.

According to another preferred embodiment of the present invention, twosides of the clutch wheel are each provided with an oil seal element, soas to prevent liquid in the clutch wheel from flowing into the outerwheel.

According to another preferred embodiment of the present invention, oneside of one of the oil seal elements is provided with a positioningmember, and the positioning member is sleeved over an inner side wallsurface of the outer wheel in a tight-fit manner, to limit axialpositions of the oil seal elements.

According to another preferred embodiment of the present invention, thepositioning member is a C-shaped retaining ring.

According to another preferred embodiment of the present invention, anend, corresponding to the second end of the hollow core shaft, of theouter wheel is arranged with a dust cover, so as to prevent externaldust from entering the outer wheel.

The present invention further provides an alternator having the pulleyaccording to the present invention.

According to another preferred embodiment of the present invention, thealternator is used on a vehicle.

For better understanding of the detailed description of the presentinvention, the features and technical advantages of the presentinvention are described generally above. The following describes theadditional features and advantages of the present invention. Personsskilled in the art should be aware that the disclosed concept andspecific implementation manner can be easily used as a basis formodifying or designing other structures for implementing objectives thesame as the present invention. Persons skilled in the art should also beaware that such equivalent structures do not depart from the spirit andscope of the present invention which are claimed in the patentapplication scope.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more thorough understanding of the present invention andadvantages of the present invention, the following descriptions areprovided with reference to the accompanying drawings, where:

FIG. 1 is a three-dimensional exploded view of a pulley for analternator according to the present invention;

FIG. 2 is a sectional assembled view of a pulley for an alternatoraccording to the present invention;

FIG. 3 is a schematic structural view of a hollow connecting shaftaccording to the present invention;

FIG. 4 is a schematic structural view of a hollow core shaft accordingto the present invention; and

FIG. 5 is a schematic view of a rotor of an alternator according to thepresent invention.

MEANING OF REFERENCE NUMERALS

-   -   10 Pulley    -   20 Joint lever    -   30 Rotor    -   110 Outer wheel    -   111 Axle hole    -   112 Belt groove    -   113 Step portion    -   120 Clutch wheel    -   121 Pivot hole    -   122 Housing    -   123 Rolling member    -   124 Elastic member    -   125 Cap    -   130 Hollow connecting shaft    -   131 First end of the hollow connecting shaft    -   132 Second end of the hollow connecting shaft    -   133 First protruding portion    -   134 Stop wall of the hollow connecting shaft    -   140 Hollow core shaft    -   141 First end of the hollow core shaft    -   142 Second end of the hollow core shaft    -   143 First ball bearing    -   144 Second ball bearing    -   145 Protruding ring of the hollow core shaft    -   146 Second protruding portion    -   147 Stop wall of the hollow core shaft    -   148 Threaded surface    -   150 Elastic element    -   160 Tight-fit component    -   161 Positioning gasket    -   162 C-shaped retaining ring    -   170 Positioning casing    -   171 Protruding ring of the positioning casing    -   181 Oil seal element    -   182 Oil seal element    -   183 Positioning member    -   184 Dust cover    -   185 Positioning member

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following embodiments describe the present invention in furtherdetail. The embodiments are merely used to describe the presentinvention and illustrate the advantages of specific embodiments of thepresent invention, but it does not mean that the present invention islimited to such implementations.

FIG. 1 and FIG. 2 are respectively a three-dimensional exploded view anda sectional assembled view of a pulley for an alternator according tothe present invention. As shown in FIG. 1 and FIG. 2, a pulley 10 for analternator according to the present invention mainly includes an outerwheel 110, a clutch wheel 120, a hollow connecting shaft 130, a hollowcore shaft 140, an elastic element 150, and a tight-fit component 160.The outer wheel 110 is a wheel-shaped member provided with an axle hole111 at the center, and is provided with a belt groove 112 on an outercircumferential wall surface thereof and a step portion 113 on an innercircumferential wall surface thereof. The clutch wheel 120 is annular,provided with a pivot hole 121 at the center, and fixedly disposed inthe axle hole 111 of the outer wheel 110. For example, a groove may beprovided in a concave manner on the inner circumferential wall surfaceof the outer wheel 110, and an anaerobic adhesive is coated in thegroove so that the clutch wheel 120 can be fixedly connected to an innercircumferential wall surface of the axle hole 111 of the outer wheel 110by means of tight fit and adhesion of the anaerobic adhesive. One end ofthe clutch wheel 120 abuts against the step portion 113 of the outerwheel 110 to limit an axial position of the clutch wheel 120 and toensure that an end surface of the clutch wheel 120 is perpendicular tothe hollow connecting shaft 130 and the hollow core shaft 140, preventaxial displacement of the clutch wheel 120 during high-speed rotation,and moreover, provide an axial positioning reference during assembly ofcomponents in the outer wheel 110, which facilitates positioning duringthe assembly.

The hollow connecting shaft 130 has a first end 131 and a second end132. The first end 131 is rotatably disposed in the clutch wheel 120 sothat the hollow connecting shaft 130 can maintain a co-rotationalrelationship with the outer wheel 110 in a first relative rotationdirection by means of the clutch wheel 120 (for example, the hollowconnecting shaft 130 rotates anticlockwise relative to the outer wheel110), and it is disassociated from the co-rotational relationship withthe outer wheel 110 in a second relative rotation direction to enter anidling state (for example, the hollow connecting shaft 130 rotatesclockwise relative to the outer wheel 110), and at this time, the hollowconnecting shaft 130 rotates independently of the outer wheel 110. Thehollow connecting shaft 130 is provided with a first protruding portion133 on the second end 132, as shown in FIG. 3.

In a preferred embodiment of the present invention, the clutch wheel 120has a housing 122, a plurality of rolling members 123, a plurality ofelastic members 124, and two caps 125. The clutch wheel 120 is providedwith a positioning member 185 on an end opposite to the end abuttingagainst the step portion 113 to limit the axial position of the clutchwheel 120 and prevent the caps 125 of the clutch wheel 120 from fallingoff. The positioning member may be a C-shaped retaining ring. For thedetailed structure and operating principle of the clutch wheel 120,reference may be made to Taiwan Patent Application No. 098129945 filedby the applicant on Sep. 4, 2009. However, the clutch wheel of thepresent invention is not limited thereto, and any speed-differenceclutch apparatus capable of implementing the functions of the clutchwheel 120 described in the present invention may be designed as theclutch wheel 120 of the present invention. Moreover, in the presentinvention, two ends of the clutch wheel 120 are each provided with anoil seal element 181/182 so as to prevent a liquid (for example, alubricating oil) in the clutch wheel 120 from permeating and pollutingthe interior of the pulley 10. Furthermore, a positioning member 183 maybe sleeved over one side of the oil seal element 182. The positioningmember 183 may be a C-shaped retaining ring, and may be sleeved over aninner side wall surface of the outer wheel 110 in a tight-fit manner, tolimit axial positions of the oil seal elements 181 and 182 and theclutch wheel 120.

The hollow core shaft 140 is disposed in the outer wheel 110 and has afirst end 141 and a second end 142. A first ball bearing 143 is sleevedover the first end 141, and a second ball bearing 144 is sleeved overthe second end 142. The first ball bearing 143 and the second ballbearing 144 are both fixedly connected to the inner circumferential wallsurface of the outer wheel 110 (for example, the outer wheel 110 may beprovided with two grooves on the inner circumferential wall surface in aconcave manner, and an anaerobic adhesive is coated in the grooves sothat the first ball bearing 143 and the second ball bearing 144 can befixedly connected to the inner circumferential wall surface of the axlehole 111 of the outer wheel 110 by means of tight fit and adhesion ofthe anaerobic adhesive) so that the hollow core shaft 140 is rotatablerelative to the outer wheel 110. In addition, the hollow core shaft 140passes through the hollow connecting shaft 130, and the first end 141 ofthe hollow core shaft 140 protrudes from the first end 131 of the hollowconnecting shaft 130. A protruding ring 145 is annularly arranged at thesecond end 142 of the hollow core shaft 140. The protruding ring 145 isrotatably arranged on the second end 132 of the hollow connecting shaft130. A second protruding portion 146 is provided in a protruding mannerin a direction towards the hollow connecting shaft 130, and the secondprotruding portion 146 corresponds to the first protruding portion 133so that after the hollow connecting shaft 130 and the hollow core shaft140 rotate by a particular degree relative to each other, the firstprotruding portion 133 of the hollow connecting shaft 130 contacts thesecond protruding portion 146 of the hollow core shaft 140, therebystopping relative rotation between the hollow connecting shaft 130 andthe hollow core shaft 140. For example, when the hollow connecting shaft130 is provided with two first protruding portions 133 at the second end132, and when the hollow core shaft 140 is provided with three secondprotruding portions 146 at the second end 142, the hollow core shaft 140can only rotate clockwise or anticlockwise by 120 degrees relative tothe hollow connecting shaft 130 after being sleeved over the hollowconnecting shaft 130 because relative rotation between the hollowconnecting shaft 130 and the hollow core shaft 140 is stopped when thefirst protruding portions 133 contact the second protruding portions146.

The elastic element 150 is disposed between the second end 132 of thehollow connecting shaft 130 and the second end 142 of the hollow coreshaft 140. In a preferred embodiment of the present invention, theelastic element is a torque spring, and a wire profile of the torquespring may be circular, elliptical, or rectangular. When the wireprofile of the torque spring is rectangular, two end surfaces of thetorque spring may be grinded so as to enhance an axial positioningcapability of the torque spring and control a free length of the springmore precisely. The hollow connecting shaft 130 is provided with a stopwall 134 in a concave manner on an inner circumferential wall surface ofthe second end 132 (as shown in FIG. 3) so that one end of the elasticelement 150 can abut against the stop wall 134, and the elastic element150 may also be fixedly connected to the stop wall 134. In addition, Thehollow core shaft 140 is also provided with a stop wall 147 on an innerside of the protruding ring 145 of the second end 142 (as shown in FIG.4) so that the other end of the elastic element 150 can abut against thestop wall 147, and the elastic element 150 may also be fixedly connectedto the stop wall 147. When the two ends of the elastic element 150 arefixedly connected to the stop wall 134 of the hollow connecting shaft130 and the stop wall 147 of the hollow core shaft 140, relativerotation between the hollow connecting shaft 130 and the hollow coreshaft 140 presses or stretches the elastic element 150; when the twoends of the elastic element 150 merely abut against but are not fixedlyconnected to the stop wall 134 of the hollow connecting shaft 130 or thestop wall 147 of the hollow core shaft 140, relative rotation betweenthe hollow connecting shaft 130 and the hollow core shaft 140 onlypresses the elastic element 150.

The tight-fit component 160 is a C-shaped retaining ring; the C-shapedretaining ring is sleeved over the outer circumferential wall surface ofthe first end 141 of the hollow core shaft 140 in a tight-fit manner,and is tightly fit with a tail end surface of the first end 131 of thehollow connecting shaft 130. Therefore, under a friction between thetight-fit component 160 and the end surface of the first end 131 of thehollow connecting shaft 130 and a friction between the tight-fitcomponent 160 and the outer circumferential wall surface of the firstend 141 of the hollow core shaft 140, the hollow connecting shaft 130and the hollow core shaft 140 drive each other and corotate coaxially,as shown in FIG. 3.

A positioning casing 170 is further sleeved over the first ball bearing143, and the positioning casing 170 is a hollow annular pipe providedwith a protruding ring 171 at one end; therefore, the protruding ring171 penetrates the first ball bearing 143 and provides an abutting andcushioning function when the pulley 10 is installed on an alternator,and an axial position of the pulley 10 on the alternator is limited bythe positioning casing 170.

The hollow core shaft 140 is provided with a threaded surface 148 on aninner circumferential wall surface thereof, the threaded surface 148 maybe screwed with a joint lever 20 having corresponding threads, and thejoint lever 20 is connected to a rotor 30 of the alternator so that thehollow core shaft 140 and the rotor 30 corotate synchronously (as shownin FIG. 5). In addition, an end, corresponding to the second end 142 ofthe hollow core shaft 140, of the outer wheel 110 is arranged with adust cover 184 so as to prevent external dust from entering the outerwheel 110.

With the structure described above, when a mechanical energy generatingsource provides an external force to drive the outer wheel 110 torotate, the outer wheel 110 rotates relative to the hollow connectingshaft 130 in the first relative rotation direction and drives, throughthe clutch wheel 120, the hollow connecting shaft 130 to rotatesynchronously, and with the friction provided by the tight-fit component160, the hollow connecting shaft 130 drives the hollow core shaft 140 torotate. At this time, if the friction provided by the tight-fitcomponent 160 is insufficient to drive the hollow core shaft 140 torotate, the hollow connecting shaft 130 rotates relative to the hollowcore shaft 140, which causes the stop wall 134 at the second end 132 ofthe hollow connecting shaft 130 to press the elastic element 150, andwhile being pressed, the elastic element 150 pushes the stop wall 147 atthe second end 142 of the hollow core shaft 140, thereby driving thehollow core shaft 140 to rotate. At this time, if a relative rotationangle between the hollow connecting shaft 130 and the hollow core shaft140 exceeds a predetermined value (for example, 120 degrees), the firstprotruding portion 133 of the hollow connecting shaft 130 contacts thesecond protruding portion 146 of the hollow core shaft 140, therebystopping relative rotation between the hollow connecting shaft 130 andthe hollow core shaft 140 so as to avoid pressing the elastic element150 excessively and damaging the structure thereof, and to set thehollow connecting shaft 130 and the hollow core shaft 140 in asynchronous co-rotational relationship; the hollow core shaft 140 alsodrives the rotor 30 to rotate so that the alternator generates aninduced current.

In addition, if the outer wheel 110 is originally in a rotation state,when the mechanical energy generating source provides an external forceto accelerate the rotation of the outer wheel 110, an operatingprinciple of the pulley 10 of the present invention is substantially thesame as the aforementioned operating principle in the case of startingthe outer wheel 110 to rotate, and therefore it is not repeated herein.

On the contrary, when the external force stops driving the outer wheel110 to rotate, the hollow core shaft 140 continues to rotate due toinertia of the rotor 30. At this time, the hollow core shaft 140 drives,by using the friction provided by the tight-fit component 160, thehollow connecting shaft 130 to rotate relative to the outer wheel 110 inthe second relative rotation direction so that the hollow connectingshaft 130 is disassociated from the co-rotational relationship with theouter wheel 110. At this time, if the friction provided by the tight-fitcomponent 160 is insufficient to drive the hollow connecting shaft 130to rotate, the hollow core shaft 140 rotates relative to the hollowconnecting shaft 130; if the elastic element 150 merely abuts againstbut is not fixedly connected to the hollow connecting shaft 130 and thehollow core shaft 140, the hollow core shaft 140 keeps rotating relativeto the hollow connecting shaft 130 until the second protruding portion146 of the hollow core shaft 140 contacts the first protruding portion133 of the hollow connecting shaft 130, thereby stopping relativerotation between the hollow connecting shaft 130 and the hollow coreshaft 140 and setting the hollow connecting shaft 130 and the hollowcore shaft 140 in a synchronous co-rotational relationship so that thehollow connecting shaft 130 and the hollow core shaft 140 rotaterelative to the outer wheel 110 in the second relative rotationdirection.

If the elastic element 150 is fixedly connected to the hollow connectingshaft 130 and the hollow core shaft 140, when the friction provided bythe tight-fit component 160 is insufficient to drive the hollowconnecting shaft 130 to rotate, the hollow core shaft 140 rotatesrelative to the hollow connecting shaft 130 and stretches the elasticelement 150, and while being stretched, the elastic element 150 pullsthe second end 132 of the hollow connecting shaft 130, thereby drivingthe hollow connecting shaft 130 to rotate relative to the outer wheel110 in the second relative rotation direction so that the hollowconnecting shaft 130 is disassociated from the co-rotationalrelationship with the outer wheel 110. At this time, if rotation of thehollow connecting shaft 130 relative to the hollow core shaft 140exceeds a predetermined value (for example, 120 degrees), the firstprotruding portion 133 of the hollow connecting shaft 130 contacts thesecond protruding portion 146 of the hollow core shaft 140, therebystopping relative rotation between the hollow connecting shaft 130 andthe hollow core shaft 140 so as to avoid stretching the elastic element150 excessively and damaging the structure thereof, and to set thehollow connecting shaft 130 and the hollow core shaft 140 in asynchronous co-rotational relationship so that the hollow connectingshaft 130 and the hollow core shaft 140 rotate relative to the outerwheel 110 in the second relative rotation direction.

In addition, if the external force driving the outer wheel 110decreases, the operating principle of the pulley 10 of the presentinvention is substantially the same as the aforementioned operatingprinciple in the case in which the outer wheel 110 stops rotating, andtherefore it is not repeated herein.

In the pulley 10 of the present invention, a belt (not shown in thefigure) may be wound on the belt groove 112 of the outer wheel 110 sothat the mechanical energy generating source can provide an externalforce to drive the belt, thereby driving the outer wheel 110 to rotate.In addition, the pulley 10 of the present invention is applicable to analternator system, such as a power generation system and an alternatorsystem of a vehicle. The pulley of the present invention is especiallysuitable to be used as a stator structure of an automotive alternator.When the pulley of the present invention is applied to an automotivealternator, the mechanical energy generating source is an automobileengine.

In a preferred embodiment of the present invention, the tight-fitcomponent 160 of the pulley 10 of the present invention may be omitted,and two ends of the elastic element 150 are fixedly connected to thestop wall 147 at the second end 142 of the hollow core shaft 140 and thestop wall 134 at the second end 132 of the hollow connecting shaft 130.In this manner, when an external force drives the outer wheel 110 torotate, the outer wheel 110 rotates relative to the hollow connectingshaft 130 in the first relative rotation direction and drives, throughthe clutch wheel 120, the hollow connecting shaft 130 to rotatesynchronously; the second end 132 of the hollow connecting shaft 130presses the elastic element 150, and while being pressed, the elasticelement 150 pushes the stop wall 147 at the second end 142 of the hollowcore shaft 140, thereby driving the hollow core shaft 140 to rotate. Atthis time, if a rotation angle of the hollow connecting shaft 130relative to the hollow core shaft 140 exceeds a predetermined value, thefirst protruding portion 133 of the hollow connecting shaft 130 contactsthe second protruding portion 146 of the hollow core shaft 140, therebystopping relative rotation between the hollow connecting shaft 130 andthe hollow core shaft 140 so as to prevent the elastic element 150 frombeing pressed excessively, setting the hollow connecting shaft 130 andthe hollow core shaft 140 in a synchronous co-rotational relationship,and drive the rotor 30 to rotate.

On the contrary, when the external force decreases or stops driving theouter wheel 110 to rotate, the hollow core shaft 140 continues to rotatedue to inertia of the rotor 30 and stretches the elastic element 150,and while being stretched, the elastic element 150 pulls the second end132 of the hollow connecting shaft 130, thereby driving the hollowconnecting shaft 130 to rotate relative to the outer wheel 110 in thesecond relative rotation direction so that the hollow connecting shaft130 is disassociated from the co-rotational relationship with the outerwheel 110 and idles in the clutch wheel 120. At this time, if a rotationangle of the hollow connecting shaft 130 relative to the hollow coreshaft 140 exceeds a predetermined value, the first protruding portion133 of the hollow connecting shaft 130 contacts the second protrudingportion 146 of the hollow core shaft 140, thereby stopping relativerotation between the hollow connecting shaft 130 and the hollow coreshaft 140 so as to prevent the elastic element 150 from being stretchedexcessively, and to set the hollow connecting shaft 130 and the hollowcore shaft 140 in a synchronous co-rotational relationship, in which thehollow connecting shaft 130 and the hollow core shaft 140 idle in theouter wheel 110. In addition, in a preferred embodiment of the presentinvention, in the pulley 10 of the present invention, the firstprotruding portion 133 and the second protruding portion 146 may not bedisposed, the protruding ring 145 at the second end 142 of the hollowcore shaft 140 is directly sleeved over the second end 132 of the hollowconnecting shaft 130, and two ends of the elastic element 150 arefixedly connected to the stop wall 147 at the second end 142 of thehollow core shaft 140 and the stop wall 134 at the second end 132 of thehollow connecting shaft 130. Therefore, when an external force drivesthe outer wheel 110 to rotate, the outer wheel 110 rotates relative tothe hollow connecting shaft 130 in the first relative rotation directionand drives, through the clutch wheel 120, the hollow connecting shaft130 to rotate synchronously, and the hollow connecting shaft 130 drives,through the tight-fit component 160, the hollow core shaft 140 torotate. At this time, if the friction provided by the tight-fitcomponent 160 is insufficient to drive the hollow core shaft 140 torotate, the stop wall 134 at the second end 132 of the hollow connectingshaft 130 presses the elastic element 150, and while being pressed, theelastic element 150 pushes the stop wall 147 at the second end 142 ofthe hollow core shaft 140, thereby driving the hollow core shaft 140 torotate, so as to drive the rotor 30 of the alternator to rotate.

On the contrary, when the external force decreases or stops driving theouter wheel 110 to rotate, the hollow core shaft 140 continues to rotatedue to inertia of the rotor 30 and drives, through the tight-fitcomponent 160, the hollow connecting shaft 130 to rotate relative to theouter wheel 110 in the second relative rotation direction. At this time,if the friction provided by the tight-fit component 160 is insufficientto drive the hollow connecting shaft 130 to rotate, the hollow coreshaft 140 stretches the elastic element 150, and while being stretched,the elastic element 150 pulls the second end 132 of the hollowconnecting shaft 130, thereby driving the hollow connecting shaft 130 torotate relative to the outer wheel 110 in the second relative rotationdirection so that the hollow connecting shaft 130 is disassociated fromthe co-rotational relationship with the outer wheel 110 and idles in theclutch wheel 120.

Further, in a preferred embodiment of the present invention, in thepulley 10 of the present invention, the tight-fit component 160, thefirst protruding portion 133, and the second protruding portion 146 maynot be disposed; the protruding ring 145 at the second end 142 of thehollow core shaft 140 is directly sleeved over the second end 132 of thehollow connecting shaft 130, and two ends of the elastic element 150 arefixedly connected to the stop wall 147 at the second end 142 of thehollow core shaft 140 and the stop wall 134 at the second end 132 of thehollow connecting shaft 130. In this manner, when an external forcedrives the outer wheel 110 to rotate, the outer wheel 110 rotatesrelative to the hollow connecting shaft 130 in the first relativerotation direction and drives, through the clutch wheel 120, the hollowconnecting shaft 130 to rotate synchronously; the stop wall 134 at thesecond end 132 of the hollow connecting shaft 130 presses the elasticelement 150, and while being pressed, the elastic element 150 pushes thestop wall 147 at the second end 142 of the hollow core shaft 140,thereby driving the hollow core shaft 140 to rotate.

On the contrary, when the external force decreases or stops driving theouter wheel 110 to rotate, the hollow core shaft 140 continues to rotatedue to inertia of the rotor 30 and stretches the elastic element 150,and while being stretched, the elastic element 150 pulls the second end132 of the hollow connecting shaft 130, thereby driving the hollowconnecting shaft 130 to rotate relative to the outer wheel 110 in thesecond relative rotation direction so that the hollow connecting shaft130 is disassociated from the co-rotational relationship with the outerwheel 110 and idles in the clutch wheel 120.

Although the present invention and advantages thereof are described indetail above, it should be understood that variations, alternativesolutions, and modifications can be made herein without departing fromthe spirit and scope of the present invention which are defined in theappended patent application scope. Moreover, the scope of the presentinvention is not limited to the specific implementations of the process,machine, product, material composition, means, method, and stepsdescribed in the specification. For example, persons skilled in the artcan easily learn from the disclosure of the present invention thatexisting or to-be-developed processes, machines, products, materialcompositions, means, methods and steps that substantially implement thesame function or substantially achieve the same result as thecorresponding implementation manner described herein may be used.Correspondingly, the appended patent application scope is intended tocover such processes, machines, products, material compositions, means,methods or steps.

We claim:
 1. A pulley for an alternator, comprising: an outer wheel,provided with an axle hole at the center; a clutch wheel, fixedlydisposed in the axle hole of the outer wheel and having a pivot hole; ahollow connecting shaft, having a first end and a second end, whereinthe first end is rotatably disposed in the pivot hole of the clutchwheel so that the hollow connecting shaft maintains a co-rotationalrelationship with the outer wheel in a first relative rotation directionby means of the clutch wheel, while in a second relative rotationdirection, the hollow connecting shaft is disassociated from theco-rotational relationship with the outer wheel and presents an idlingstate; and the second end of the hollow connecting shaft is providedwith a first protruding portion; a hollow core shaft, having a first endand a second end, wherein the hollow core shaft is rotatably received inthe outer wheel, and the second end of the hollow core shaft isrotatably arranged at the second end of the hollow connecting shaft; thesecond end of the hollow core shaft is provided with a second protrudingportion, and the second protruding portion corresponds to the firstprotruding portion; the number of one of the first protruding portionand the second protruding portion is at least one, and the number of theother of the first protruding portion and the second protruding portionis at least two; and an elastic element, disposed between the second endof the hollow connecting shaft and the second end of the hollow coreshaft; wherein when an external force drives the outer wheel to rotate,the outer wheel rotates relative to the hollow connecting shaft in thefirst relative rotation direction and drives, through the clutch wheel,the hollow connecting shaft to rotate synchronously; the second end ofthe hollow connecting shaft presses the elastic element, and while beingpressed, the elastic element pushes the second end of the hollow coreshaft, thereby driving the hollow core shaft to rotate; and if arotation angle of the hollow connecting shaft relative to the hollowcore shaft exceeds a predetermined value at this time, the firstprotruding portion of the hollow connecting shaft contacts the secondprotruding portion of the hollow core shaft, thereby stopping relativerotation between the hollow connecting shaft and the hollow core shaftso as to prevent the elastic element from being pressed excessively andto set the hollow connecting shaft and the hollow core shaft in asynchronous co-rotational relationship; and when the external forcedecreases or stops driving the outer wheel to rotate, the hollow coreshaft continues to rotate due to inertia, and stretches the elasticelement, and while being stretched, the elastic element pulls the secondend of the hollow connecting shaft, thereby driving the hollowconnecting shaft to rotate relative to the outer wheel in the secondrelative rotation direction so that the hollow connecting shaft isdisassociated from the co-rotational relationship with the outer wheeland idles in the clutch wheel; and if a rotation angle of the hollowconnecting shaft relative to the hollow core shaft exceeds apredetermined value at this time, the first protruding portion of thehollow connecting shaft contacts the second protruding portion of thehollow core shaft, thereby stopping relative rotation between the hollowconnecting shaft and the hollow core shaft so as to prevent the elasticelement from being stretched excessively and to set the hollowconnecting shaft and the hollow core shaft in a synchronousco-rotational relationship.
 2. The pulley for an alternator according toclaim 1, wherein the hollow core shaft passes through the hollowconnecting shaft, and the first end of the hollow core shaft protrudesfrom the first end of the hollow connecting shaft; a tight-fit componentis sleeved over an outer circumferential wall surface of the first endof the hollow core shaft in a tight-fit manner, and the tight-fitcomponent is also tightly fit with an end surface of the first end ofthe hollow connecting shaft; the hollow connecting shaft and the hollowcore shaft are made to corotate coaxially under a friction between thetight-fit component and the hollow connecting shaft and a frictionbetween the tight-fit component and the hollow core shaft, and when theexternal force decreases or stops driving the outer wheel to rotate, thehollow core shaft continues to rotate due to inertia and drives, throughthe tight-fit component, the hollow connecting shaft to rotate relativeto the outer wheel in the second relative rotation direction so that thehollow connecting shaft is disassociated from the co-rotationalrelationship with the outer wheel and idles in the clutch wheel, andwherein the tight-fit component is a C-shaped retaining ring.
 3. Thepulley for an alternator according to claim 1, wherein a first ballbearing is sleeved over the first end of the hollow core shaft, a secondball bearing is sleeved over the second end of the hollow core shaft,and the first ball bearing and the second ball bearing are disposedbetween the hollow core shaft and the outer wheel so that the hollowcore shaft is rotatable relative to the outer wheel.
 4. The pulley foran alternator according to claim 3, wherein three grooves are providedin a concave manner on an inner circumferential wall surface of theouter wheel, and an anaerobic adhesive is coated in the grooves so thatthe clutch wheel, the first ball bearing, and the second ball bearingare separately tightly fit in the grooves and are fixedly glued in theouter wheel by using the anaerobic adhesive, and wherein a positioningcasing is further sleeved over the first ball bearing, and an axialposition of the pulley on the alternator is limited by the positioningcasing.
 5. The pulley for an alternator according to claim 1, wherein anouter circumferential wall surface of the outer wheel is provided with abelt groove for a belt to be wound on, wherein the belt is connected toa mechanical energy generating source, and the mechanical energygenerating source provides an external force to drive the belt, therebydriving the outer wheel to rotate, and wherein the mechanical energygenerating source is an engine.
 6. The pulley for an alternatoraccording to claim 1, wherein an inner circumferential wall surface ofthe hollow core shaft is provided with a threaded surface, the threadedsurface is screwed with a joint lever having corresponding threads, andthe joint lever is connected to a rotor so that the hollow core shaftand the rotor corotate synchronously.
 7. The pulley for an alternatoraccording to claim 1, wherein an inner circumferential wall surface ofthe outer wheel is provided with a step portion, for the clutch wheel toabut against, thereby limiting an axial displacement of the clutchwheel.
 8. The pulley for an alternator according to claim 1, wherein oneend of the clutch wheel is provided with a positioning member to limitan axial position of the clutch wheel, and wherein the positioningmember is a C-shaped retaining ring.
 9. The pulley for an alternatoraccording to claim 1, wherein the elastic element is a torque spring,and a wire profile of the torque spring is circular, elliptical, orrectangular, and wherein when the wire profile of the torque spring isrectangular, two end surfaces of the torque spring are grinded so as toenhance axial positioning of the torque spring and control a free lengthof the torque spring more precisely.
 10. The pulley for an alternatoraccording to claim 1, wherein two sides of the clutch wheel are eachprovided with an oil seal element so as to prevent liquid in the clutchwheel from flowing into the outer wheel, and wherein one side of one ofthe oil seal elements is provided with a positioning member, and thepositioning member is sleeved over an inner side wall surface of theouter wheel in a tight-fit manner to limit axial positions of the oilseal elements, and the positioning member is a C-shaped retaining ring.11. The pulley for an alternator according to claim 1, wherein an end,corresponding to the second end of the hollow core shaft, of the outerwheel is arranged with a dust cover so as to prevent external dust fromentering the outer wheel.
 12. A pulley for an alternator, comprising: anouter wheel, provided with an axle hole at the center; a clutch wheel,fixedly disposed in the axle hole of the outer wheel and having a pivothole; a hollow connecting shaft, having a first end and a second end,wherein the first end is rotatably disposed in the pivot hole of theclutch wheel so that the hollow connecting shaft maintains aco-rotational relationship with the outer wheel in a first relativerotation direction by means of the clutch wheel, while in a secondrelative rotation direction, the hollow connecting shaft isdisassociated from the co-rotational relationship with the outer wheel,and presents an idling state; and the second end of the hollowconnecting shaft is provided with a first protruding portion; a hollowcore shaft, having a first end and a second end, wherein the hollow coreshaft is rotatably received in the outer wheel, and the hollow coreshaft passes through the hollow connecting shaft; the first end of thehollow core shaft protrudes from the first end of the hollow connectingshaft, and the second end of the hollow core shaft is rotatably arrangedon the second end of the hollow connecting shaft; the second end of thehollow core shaft is provided with a second protruding portion, and thesecond protruding portion corresponds to the first protruding portion;the number of one of the first protruding portion and the secondprotruding portion is at least one, and the number of the other of thefirst protruding portion and the second protruding portion is at leasttwo; an elastic element, disposed between the second end of the hollowconnecting shaft and the second end of the hollow core shaft; and atight-fit component, sleeved over an outer circumferential wall surfaceof the first end of the hollow core shaft in a tight-fit manner andtightly fit with an end surface of the first end of the hollowconnecting shaft so that the hollow connecting shaft and the hollow coreshaft corotate coaxially under a friction between the tight-fitcomponent and the hollow connecting shaft and a friction between thetight-fit component and the hollow core shaft; wherein when an externalforce drives the outer wheel to rotate, the outer wheel rotates relativeto the hollow connecting shaft in the first relative rotation directionand drives, through the clutch wheel, the hollow connecting shaft torotate synchronously, and the hollow connecting shaft drives, throughthe tight-fit component, the hollow core shaft to rotate; if thefriction provided by the tight-fit component is insufficient to drivethe hollow core shaft to rotate at this time, the second end of thehollow connecting shaft presses the elastic element, and while beingpressed, the elastic element pushes the second end of the hollow coreshaft, thereby driving the hollow core shaft to rotate; and if arotation angle of the hollow connecting shaft relative to the hollowcore shaft exceeds a predetermined value at this time, the firstprotruding portion of the hollow connecting shaft contacts the secondprotruding portion of the hollow core shaft, thereby stopping relativerotation between the hollow connecting shaft and the hollow core shaftso as to prevent the elastic element from being pressed excessively andto set the hollow connecting shaft and the hollow core shaft in asynchronous co-rotational relationship; and when the external forcedecreases or stops driving the outer wheel to rotate, the hollow coreshaft continues to rotate due to inertia and drives, through thetight-fit component, the hollow connecting shaft to rotate relative tothe outer wheel in the second relative rotation direction; and if thefriction provided by the tight-fit component is insufficient to drivethe hollow connecting shaft to rotate at this time, the hollow coreshaft rotates relative to the hollow connecting shaft until the firstprotruding portion of the hollow connecting shaft contacts the secondprotruding portion of the hollow core shaft, thereby stopping relativerotation between the hollow connecting shaft and the hollow core shaftand setting the hollow connecting shaft and the hollow core shaft in asynchronous co-rotational relationship.
 13. The pulley for an alternatoraccording to claim 12, wherein when the external force decreases orstops driving the outer wheel to rotate, the hollow core shaft continuesto rotate due to inertia and drives, through the tight-fit component,the hollow connecting shaft to rotate relative to the outer wheel in thesecond relative rotation direction; if the friction provided by thetight-fit component is insufficient to drive the hollow connecting shaftto rotate at this time, the hollow core shaft stretches the elasticelement, and while being stretched, the elastic element pulls the secondend of the hollow connecting shaft, thereby driving the hollowconnecting shaft to rotate relative to the outer wheel in the secondrelative rotation direction so that the hollow connecting shaft isdisassociated from the co-rotational relationship with the outer wheel;and if a rotation angle of the hollow connecting shaft relative to thehollow core shaft exceeds a predetermined value, the protruding portionof the hollow connecting shaft contacts the protruding portion of thehollow core shaft, thereby stopping relative rotation between the hollowconnecting shaft and the hollow core shaft so as to prevent the elasticelement from being stretched excessively and to set the hollowconnecting shaft and the hollow core shaft in a synchronousco-rotational relationship.
 14. The pulley for an alternator accordingto claim 12, wherein a first ball bearing is sleeved over the first endof the hollow core shaft, a second ball bearing is sleeved over thesecond end of the hollow core shaft, and the first ball bearing and thesecond ball bearing are disposed between the hollow core shaft and theouter wheel so that the hollow core shaft is rotatable relative to theouter wheel.
 15. The pulley for an alternator according to claim 14,wherein three grooves are provided in a concave manner on an innercircumferential wall surface of the outer wheel, and an anaerobicadhesive is coated in the grooves so that the clutch wheel, the firstball bearing, and the second ball bearing are separately tightly fit inthe grooves and are fixedly glued in the outer wheel by using theanaerobic adhesive, and wherein a positioning casing is further sleevedover the first ball bearing, and an axial position of the pulley on thealternator is limited by the positioning casing.
 16. The pulley for analternator according to claim 12, wherein an outer circumferential wallsurface of the outer wheel is provided with a belt groove for a belt tobe wound on, wherein the belt is connected to a mechanical energygenerating source, and the mechanical energy generating source providesan external force to drive the belt, thereby driving the outer wheel torotate, and wherein the mechanical energy generating source is anengine.
 17. The pulley for an alternator according to claim 12, whereinan inner circumferential wall surface of the hollow core shaft isprovided with a threaded surface, the threaded surface is screwed with ajoint lever having corresponding threads, and the joint lever isconnected to a rotor, so that the hollow core shaft and the rotorcorotate synchronously.
 18. The pulley for an alternator according toclaim 12, wherein an inner circumferential wall surface of the outerwheel is provided with a step portion, for the clutch wheel to abutagainst, thereby limiting an axial displacement of the clutch wheel. 19.The pulley for an alternator according to claim 12, wherein thetight-fit component is a C-shaped retaining ring, and wherein one end ofthe clutch wheel is provided with a positioning member to limit an axialposition of the clutch wheel, and the positioning member is a C-shapedretaining ring.
 20. The pulley for an alternator according to claim 12,wherein the elastic element is a torque spring, and a wire profile ofthe torque spring is circular, elliptical, or rectangular, and whereinwhen the wire profile of the torque spring is rectangular, two endsurfaces of the torque spring are grinded so as to enhance axialpositioning of the torque spring and control a free length of the torquespring more precisely.
 21. The pulley for an alternator according toclaim 12, wherein two sides of the clutch wheel are each provided withan oil seal element so as to prevent liquid in the clutch wheel fromflowing into the outer wheel, and wherein one side of one of the oilseal elements is provided with a positioning member, and the positioningmember is sleeved over an inner side wall surface of the outer wheel ina tight-fit manner to limit axial positions of the oil seal elements,and the positioning member is a C-shaped retaining ring.
 22. The pulleyfor an alternator according to claim 12, wherein an end, correspondingto the second end of the hollow core shaft, of the outer wheel isarranged with a dust cover so as to prevent external dust from enteringthe outer wheel.